Because of the complex nature of the procedures we shall, in general, continue the format of investigations conducted previously. Alterations in the metabolic pool at the site of both aqueous humor and cerebrospinal fluid production in groups of sham-operated animals and in animals in which superior cervical ganglionectomy (post-ganglionic) has been performed will be studied. That supersensitivity to catecholamines takes place in animals so operated (sympathectomized) has been shown previously in this and other laboratories. Ocular pressure and pupil diameter will be measured following drug administration. We shall evaluate the effects of (1) topical norepinephrine (NE), (2) NE preceded by topical indomethacin, and (3) NE preceded by intravenous phenoxybenzamine. Both short term and long term effects of these drugs will be evaluated. At the termination of the study the animals will be anesthetized and jugular vein blood, cerebrospinal fluid and aqueous humor samples removed and the eyes enucleated for both prostaglandin and cyclic nucleotide analyses. The animals will then be decapitated and brain tissues removed for cyclic nucleotide analyses. The purpose of these studies will be to evaluate the role played by the sympathetic nervous system with respect to both ocular and brain blood-tissue barriers as well as to evaluate the altered status of metabolism in other ocular tissues.